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  • Thread-safe blocking queue implementation on .NET

    - by Shrike
    Hello. I'm looking for an implementation of thread-safe blocking queue for .NET. By "thread-safe blocking queue" I mean: - thread-safe access to a queue where Dequeue method call blocks a thread untill other thread puts (Enqueue) some value. By the moment I'v found this one: http://www.eggheadcafe.com/articles/20060414.asp (But it's for .NET 1.1). Could someone comment/criticize correctness of this implementation. Or suggest some another one. Thanks in advance.

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  • Minimizing Java Thread Context Switching Overhead

    - by binil
    I have a Java application running on Sun 1.6 32-bit VM/Solaris 10 (x86)/Nahelem 8-core(2 threads per core). A specific usecase in the application is to respond to some external message. In my performance test environment, when I prepare and send the response in the same thread that receives the external input, I get about 50 us advantage than when I hand off the message to a separate thread to send the response. I use a ThreadPoolExecutor with a SynchronousQueue to do the handoff. In your experience what is the acceptable delay between scheduling a task to a thread pool and it getting picked up for execution? What ideas had worked for you in the past to try improve this?

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  • Multiple things at once (Threads?)

    - by Jonathan
    All, What is a really simple way of having a program do more than one thing at once, even if the computer does not necessarily have multiple 'cores'. Can I do this by creating more than one Thread? My goal is to be able to have two computers networked (through Sockets) to respond to each-other's requests, while my program will at the same time be able to be managing a UI. I want the server to potentially handle more than one client at the same time as well. My understanding is that the communication is done with BufferedReader.readLine() and PrintWriter.println(). My problem is that I want the server to be waiting on multiple readLine() requests, and also be doing other things. How do I handle this? Many thanks, Jonathan

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  • Threading Problems in ActionScript 2.0?

    - by yar
    Is it possible to have concurrency problems (thread competition) in an onEnterFrame method in ActionScript 2.0? I have written this cheesy code as a guard: if (!busy) { // I suspect some threading problems: is that even possible in flash busy = true; movePanels(); busy = false; } but this is no assurance against thread competition. If so, how can I do a basic semaphore/lock? Note: I suspect threading problems in my app, but if they're impossible, I'll check my code differently.

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  • throwing exception from APCProc crashes program

    - by lazy_banana
    I started to do some research on how terminate a multithreaded application properly and I found those 2 post(first, second) about how to use QueueUserAPC to signal other threads to terminate. I thought I should give it a try, and the application keeps crashing when I throw the exception from the APCProc. Code: #include <stdio.h> #include <windows.h> class ExitException { public: char *desc; DWORD exit_code; ExitException(char *desc,int exit_code): desc(desc), exit_code(exit_code) {} }; //I use this class to check if objects are deconstructed upon termination class Test { public: char *s; Test(char *s): s(s) { printf("%s ctor\n",s); } ~Test() { printf("%s dctor\n",s); } }; DWORD CALLBACK ThreadProc(void *useless) { try { Test t("thread_test"); SleepEx(INFINITE,true); return 0; } catch (ExitException &e) { printf("Thread exits\n%s %lu",e.desc,e.exit_code); return e.exit_code; } } void CALLBACK exit_apc_proc(ULONG_PTR param) { puts("In APCProc"); ExitException e("Application exit signal!",1); throw e; return; } int main() { HANDLE thread=CreateThread(NULL,0,ThreadProc,NULL,0,NULL); Sleep(1000); QueueUserAPC(exit_apc_proc,thread,0); WaitForSingleObject(thread,INFINITE); puts("main: bye"); return 0; } My question is why does this happen? I use mingw for compilation and my OS is 64bit. Can this be the reason?I read that you shouldn't call QueueApcProc from a 32bit app for a thread which runs in a 64bit process or vice versa, but this shouldn't be the case.

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  • Progressbar behaves strangely

    - by wanderameise
    I just created an application in C# that uses a thread which polls the UART for a receive event. If data is received an event is triggered in my main thread (GUI) and a progress bar is controlled via PerformStep() method (of course, I previously set the Max value accordingly). PerformStep is invoked using the following expression to handle cross threading this.Invoke((Action)delegate{progressBar2.PerformStep();}) When running this application the progressbar never hits its final value. It stops at 80%. When debugging and stopping at the line mentioned above, everything works fine using single steps. I have no idea what is going one! Start read thread on main thread: pThreadWrite = new Thread(new ThreadStart(ReadThread)); pThreadWrite.Start(); Read Thread: private void ReadThread() { while(1) { if (ReceiveEvent) { FlashProgressBar(); } } } Event that is triggered in main thread: private void FlashProgressBar() { this.Invoke((Action)delegate { progressBar2.PerformStep();}); } (It's a simplified representation of my code) It seems as if the internal progress is faster than the visual one.

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  • boost thread pool

    - by Dtag
    I need a threadpool for my application, and I'd like to rely on standard (C++11 or boost) stuff as much as possible. I realize there is an unofficial(!) boost thread pool class, which basically solves what I need, however I'd rather avoid it because it is not in the boost library itself -- why is it still not in the core library after so many years? In some posts on this page and elsewhere, people suggested using boost::asio to achieve a threadpool like behavior. At first sight, that looked like what I wanted to do, however I found out that all implementations I have seen have no means to join on the currently active tasks, which makes it useless for my application. To perform a join, they send stop signal to all the threads and subsequently join them. However, that completely nullifies the advantage of threadpools in my use case, because that makes new tasks require the creation of a new thread. What I want to do is: ThreadPool pool(4); for (...) { for (int i=0;i<something;i++) pool.pushTask(...); pool.join(); // do something with the results } Can anyone suggest a solution (except for using the existing unofficial thread pool on sourceforge)? Is there anything in C++11 or core boost that can help me here? Thanks a lot

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  • Cleanest Way to Invoke Cross-Thread Events

    - by Nick
    I find that the .NET event model is such that I'll often be raising an event on one thread and listening for it on another thread. I was wondering what the cleanest way to marshal an event from a background thread onto my UI thread is. Based on the community suggestions, I've used this: // earlier in the code mCoolObject.CoolEvent+= new CoolObjectEventHandler(mCoolObject_CoolEvent); // then private void mCoolObject_CoolEvent(object sender, CoolObjectEventArgs args) { if (InvokeRequired) { CoolObjectEventHandler cb = new CoolObjectEventHandler( mCoolObject_CoolEvent); Invoke(cb, new object[] { sender, args }); return; } // do the dirty work of my method here }

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  • Why is volatile not considered useful in multithreaded C or C++ programming?

    - by Michael E
    As demonstrated in this answer I recently posted, I seem to be confused about the utility (or lack thereof) of volatile in multi-threaded programming contexts. My understanding is this: any time a variable may be changed outside the flow of control of a piece of code accessing it, that variable should be declared to be volatile. Signal handlers, I/O registers, and variables modified by another thread all constitute such situations. So, if you have a global int foo, and foo is read by one thread and set atomically by another thread (probably using an appropriate machine instruction), the reading thread sees this situation in the same way it sees a variable tweaked by a signal handler or modified by an external hardware condition and thus foo should be declared volatile (or, for multithreaded situations, accessed with memory-fenced load, which is probably a better a solution). How and where am I wrong?

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  • Repeated host lookups failing in urllib2

    - by reve_etrange
    I have code which issues many HTTP GET requests using Python's urllib2, in several threads, writing the responses into files (one per thread). During execution, it looks like many of the host lookups fail (causing a name or service unknown error, see appended error log for an example). Is this due to a flaky DNS service? Is it bad practice to rely on DNS caching, if the host name isn't changing? I.e. should a single lookup's result be passed into the urlopen? Exception in thread Thread-16: Traceback (most recent call last): File "/usr/lib/python2.6/threading.py", line 532, in __bootstrap_inner self.run() File "/home/da/local/bin/ThreadedDownloader.py", line 61, in run page = urllib2.urlopen(url) # get the page File "/usr/lib/python2.6/urllib2.py", line 126, in urlopen return _opener.open(url, data, timeout) File "/usr/lib/python2.6/urllib2.py", line 391, in open response = self._open(req, data) File "/usr/lib/python2.6/urllib2.py", line 409, in _open '_open', req) File "/usr/lib/python2.6/urllib2.py", line 369, in _call_chain result = func(*args) File "/usr/lib/python2.6/urllib2.py", line 1170, in http_open return self.do_open(httplib.HTTPConnection, req) File "/usr/lib/python2.6/urllib2.py", line 1145, in do_open raise URLError(err) URLError: <urlopen error [Errno -2] Name or service not known>

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  • How do I wait for all other threads to finish their tasks?

    - by Mike
    I have several threads consuming tasks from a queue using something similar to the code below. The problem is that there is one type of task which cannot run while any other tasks are being processed. Here is what I have: while (true) // Threaded code { while (true) { lock(locker) { if (close_thread) return; task = GetNextTask(); // Get the next task from the queue } if (task != null) break; wh.WaitOne(); // Wait until a task is added to the queue } task.Run(); } And this is kind of what I need: while (true) { while (true) { lock(locker) { if (close_thread) return; if (disable_new_tasks) { task = null; } else { task = GetNextTask(); } } if (task != null) break; wh.WaitOne(); } if(!task.IsThreadSafe()) { // I would set this to false inside task.Run() at // the end of the non-thread safe task disable_new_tasks = true; Wait_for_all_threads_to_finish_their_current_tasks(); } task.Run(); } The problem is I don't know how to achive this without creating a mess.

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  • Why wait should always be in synchronized block

    - by diy
    Hi gents, We all know that in order to invoke Object.wait() , this call must be placed in synchronized block,otherwise,IllegalMonitorStateException is thrown.But what's the reason for making this restriction?I know that wait() releases the monitor, but why do we need to explicitly acquire the monitor by making particular block synchronized and then release the monitor by calling wait() ? What is the potential damage if it was possible to invoke wait() outside synch block, retaining it's semantics - suspending the caller thread ? Thanks in advance

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  • how to emulate thread local storage at user space in C++ ?

    - by vprajan
    I am working on a mobile platform over Nucleus RTOS. It uses Nucleus Threading system but it doesn't have support for explicit thread local storage i.e, TlsAlloc, TlsSetValue, TlsGetValue, TlsFree APIs. The platform doesn't have user space pthreads as well. I found that __thread storage modifier is present in most of the C++ compilers. But i don't know how to make it work for my kind of usage. How does __thread keyword can be mapped with explicit thread local storage? I read many articles but nothing is so clear for giving me the following basic information will __thread variable different for each thread ? How to write to that and read from it ? does each thread has exactly one copy of the variable ? following is the pthread based implementation: pthread_key_t m_key; struct Data : Noncopyable { Data(T* value, void* owner) : value(value), owner(owner) {} int* value; }; inline ThreadSpecific() { int error = pthread_key_create(&m_key, destroy); if (error) CRASH(); } inline ~ThreadSpecific() { pthread_key_delete(m_key); // Does not invoke destructor functions. } inline T* get() { Data* data = static_cast<Data*>(pthread_getspecific(m_key)); return data ? data->value : 0; } inline void set(T* ptr) { ASSERT(!get()); pthread_setspecific(m_key, new Data(ptr, this)); } How to make the above code use __thread way to set & get specific value ? where/when does the create & delete happen? If this is not possible, how to write custom pthread_setspecific, pthread_getspecific kind of APIs. I tried using a C++ global map and index it uniquely for each thread and retrieved data from it. But it didn't work well.

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  • Unload event for the default AppDomain?

    - by Zor
    Hi, I need to have an event fired whenever any AppDomain unloads - including the default one of the process. The problem with AppDomain.DomainUnload is that it only fires for non-default AppDomains. Furthermore, AppDomain.ProcessExit has limited execution time, which I cannot rely on. Any suggestions as to how I can achieve this would be greatly appreciated! (Alternatively, having an event fired when a background thread (Thread.IsBackground == True) works too.) Thanks in advance.

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  • Using locks inside a loop

    - by Xaqron
    // Member Variable private readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile shared int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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  • Failing faster when URL content is not found, howto

    - by Jam
    I have a thread pool that loops over a bunch of pages and checks to see if some string is there or not. If String is found, or not found response is near instant, however if server is offline or application is not running getting a rejection seems to take seconds How can I change my code to fail faster? for (Thread thread : pool) { thread.start(); } for (Thread thread : pool) { try { thread.join(); } catch (InterruptedException e) { e.printStackTrace(); } } Here is my run method @Override public void run() { for (Box b : boxes) { try { connection = new URL(b.getUrl()).openConnection(); scanner = new Scanner(connection.getInputStream()); scanner.useDelimiter("\\Z"); content = scanner.next(); if (content.equals("YES")) { } else { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } catch (Exception ex) { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } }

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  • How do I know if a boost thread is done ?

    - by jules
    I am using boost::thread to process messages in a queue. When a first message comes I start a message processing thread. When a second message comes I check if the message processing thread is done. if it is done I start a new one if it is not done I don nothing. How do I know if the thread is done ? I tried with joinable() but it is not working, as when the thread is done, it is still joinable. I also tried to interrupt the process at once, and add an interruption point at the end of my thread, but it did not work. Thanks

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  • Java Thread - Synchronization issue

    - by Yatendra Goel
    From Sun's tutorial: Synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods. (An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed) This strategy is effective, but can present problems with liveness, as we'll see later in this lesson. Q1. Is the above statements mean that if an object of a class is going to be shared among multiple threads, then all instance methods of that class (except getters of final fields) should be made synchronized, since instance methods process instance variables?

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  • Python Terminated Thread Cannot Restart

    - by Mel Kaye
    Hello, I have a thread that gets executed when some action occurs. Given the logic of the program, the thread cannot possibly be started while another instance of it is still running. Yet when I call it a second time, I get a "RuntimeError: thread already started" error. I added a check to see if it is actually alive using the Thread.is_alive() function, and it is actually dead. What am I doing wrong? I can provide more details as are needed.

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  • Understanding java's native threads and the jvm

    - by Moev4
    I understand that the jvm is itself an application that turns the bytecode of the java executable into native machine code, but when using native threads I have some questions that I just cannot seem to answer. Does every thread create their own instance of the jvm to handle their particular execution? If not then does the jvm have to have some way to schedule which thread it will handle next, if so wouldn't this render the multi-threaded nature of java useless since only one thread can be ran at a time?

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  • Where to begin with multi-threaded programming with c++?

    - by zoke
    I'm trying to implement my own IRC client as a personal proejct and I realized I needed a way to read and write from the socket at the same time. I realized I could have a reading thread which reads from the socket in the background and puts data in a queue and I could have another thread which writes data from a queue to the socket. However I have no idea on how to start with multithreaded programing or how to do it with c++. Where do I go from here?

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